Check valves are used to control flow of fluids, such as liquids or gases, in devices. For example, check valves can be used to control flow of gases and liquids in fluid systems of medical instruments, industrial process control equipment, medical devices (including implanted devices), mixing apparatus and chromatography. Most types of check valves are on/off valves for the flow of fluid. Check valves also prevent inadvertent mixing and prevent back flow of fluids. Typically in a check valve, there is a valve plug which can be moved to either block the flow or permit the flow of the fluid out of a channel. The valve plug can be moved in a variety of manners such as by fluid pressure moving it to block or unblock a channel containing the fluid. Alternately, the valve plug can be moved by electromagnetic, electrostatic, thermal, stress or other forces either alone on in combination with the fluid pressure.
US Published patent application 2005/0004250 to Hasselbrink Jr. et al. discloses a monolithic polymer element for flow control in a microfluidic device. A free-moving valve plug can be moved by control pressure in one micro channel to either block or unblock flow of the operative fluid in another intersecting micro channel. Also in US 2005/0004250, another valve plug can be moved against or away from an opening in a channel to either block or unblock the channel.
A publication by Unger et al. in Science magazine 288, 113-116 of April 2000 discloses control of fluid flow in micro channels. There are soft elastomer control lines that intersect the microfluidic channels fabricated in an elastomeric substrate material. Applying pressure to the externals surfaces of the control lines causes them to deform, closing off the part of the channel they intersect.
While the foregoing valve mechanisms are effective, further improvements are need to simplify manufacture and provide miniature check valves.
Accordingly, an object of the present invention is to provide a miniature check valve that can be made by an inexpensive manufacturing process.
Another object of the present invention is to provide a process for manufacturing a miniature check valve.